WASHINGTON — Sick Vietnam War sailors seeking federal disability benefits because of exposure to Agent Orange hit two familiar roadblocks Wednesday — congressional worries over the cost and a reluctant U.S. Department of Veterans Affairs.

Veterans say they may have been exposed to dangerous herbicide chemicals found in Agent Orange. Advocates for the veterans say the exposure likely happened via the drinking water aboard large Navy ships.

The “blue water” sailors, named for the open seas off the coast of Vietnam where they served, don’t receive the same exposure-related disability benefits as troops and pilots who served in Vietnam.

The House disability benefits subcommittee heard their plight Wednesday. But the chairman, U.S. Rep. Mike Bost, R-Ill., said there’s still no widely accepted plan among members of Congress how to pay for the aid, which could billions over the next 10 years.

Not only is the money a concern, but so is the VA’s stance.

The science some veteran advocates are relying on is just too uncertain to prove Agent Orange is causing illnesses for the sailors, said Beth Murphy, VA director of compensation service.

Murphy said the VA also sees retroactively applying the Agent Orange exposure benefits for Navy veterans, as House legislation proposes, would be too labor-intensive and complicated.

Administrative costs, actual benefit payments and other expenses associated with the bill, Murphy said, could end up costing more than $5 billion over the next 10 years.

John Wells, a retired Navy commander and now a private attorney from Louisiana advocating for the veterans, countered that figure is inflated and conflicts with what estimates of about $1 billion previously prepared by the Congressional Budget Office. He said the federal government will have problems paying for future toxic exposure benefit claims if it doesn’t start dealing with the issue now.

That’s the one area he and officials at the VA seemed to agree on during Wednesday’s hearing.

Witnesses for the VA and veterans acknowledged the U.S. military hasn’t historically kept adequate records of possible environmental dangers to active-duty personnel, impeding the federal government’s ability to later judge what type of medical help or disability payments a veteran should get.

For Vietnam veterans, neither the military nor the VA have specific exposure information for individuals who served, said Dr. Ralph Erickson, a 32-year Army veteran and medical doctor who now oversees post-deployment health issues as chief consultant for the VA.

To head off conflicts like this in the future, the two departments are working on a new program to gather toxic exposure data. The health tracking program is called the “Individual Longitudinal Exposure Record.”

The goal is to get “real time” metrics on environmental hazards where military personnel serve, Erickson said.

One example of such toxic dangers is already known. Tens of thousands of veterans who served in Iraq and Afghanistan have reported severe respiratory problems linked to burn pits, large areas where the military burned garbage and debris on base.

Bost said the veterans affairs committee could look at the cost of new and old toxic exposure benefits comprehensively. Veterans, he said, need to “have to have as few as hoops as possible to jump through” to get VA medical care and benefits.

For the past decade, Wells, along with most of the nation’s largest veteran advocacy groups, have said the VA’s exclusion of “blue water” Navy Vietnam veterans is unjust and arbitrary. They point to federally-funded research and international studies that suggest possible routes of exposure at-sea to dangerous Agent Orange herbicide chemicals. The VA says the science behind that claim is inconclusive and officials want more proof the sailors were exposed.

That proof may never come: U.S. Department of Defense didn’t collect water samples on the war-time Navy ships or from the territorial seas surrounding Vietnam where Agent Orange was extensively sprayed.

Instead, the fight for the benefits continues even five decades since the war ended and more than 25 years since Congress passed the Agent Orange Act, a broad law providing for VA disability benefits to sick Vietnam veterans.

Wells said he’ll take his pitch to other U.S. House committees working on the federal budget and tax issues. He also plans to meet with VA Secretary David Shulkin April 21.

“They have to find an offset,” Wells said. “I don’t believe that there’s sufficient money left in the VA budget to do that. That’s why we have proposed basically a ($10) filing fee for a tax return to raise money not just for the Blue Water Navy (benefits) but for all the victims of toxic exposure.”